From a physico-operational point of view, a radar function is aimed at detecting and locating the hardware objects situated in a, more or less distant, environment of a carrier. Among these objects are obviously the platforms or the vehicles situated in this environment. This point of view can be supplemented with depictions of the environment according to other domains of physical objects. Among the latter are radar transmissions originating from other platforms. An “Electronic Support Measure” or “ESM” function is aimed specifically at taking an interest in these radar transmission objects. Interest is at least twofold since, on the one hand, a depiction according to various domains ensures a consolidated perception of the environment, which is both more reliable and more robust, and on the other hand, the diversity of the characteristics of radar transmissions has implied that an ESM function possesses a fairly remarkable non-cooperative identification capability (“NCTR: Non Cooperative Target Recognition”).
It is often beneficial to supplement one or more radar functions with an ESM function for better perception of the observed scene. The joint use of radar and ESM techniques is indeed able to provide information of such a nature as to classify, or indeed to identify, a target when the latter is equipped with a transmitting radar.
Customarily, the radar function and ESM function are obtained by integrating on the carrier distinct items of equipment having strictly no common hardware element, operating over fairly different frequency ranges. Each item of equipment possesses its own devices, be they antennal, for reception or transmission, and processing, thereby increasing the volume, the mass and the cost of the whole. Moreover, this architecture complicates integration on the carrier and always poses problems of electromagnetic compatibility between the radar functions and the ESM function, since the latter is on principle done so as to receive the transmissions of the radars.
Typically, if the aircraft must be equipped with a radar function and with an ESM function, the ESM coverage is ensured by very wideband antennas with low gain disposed on the skin of the aircraft so as to cover 360°, while the radar function is carried out with the aid of a specific antennal structure, able to operate by mechanical scanning or electronic scanning. There also exist other possibilities implementing array antennas with a very wideband radiating element and which are associated with a large number of transmission-reception pathways.
On carriers of small size, integration and cost constraints may prohibit the incorporation of such functions.
Consequently, there is still to date a need for a system that is simultaneously satisfactory in respect of all the aforementioned requirements, in terms of radar function and ESM function, of their electromagnetic compatibility, of constrained volume, mass and cost.